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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

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Without interrupting the current, the cell is then lowered, the electrodes
being washed as they emerge ; the cathode is next detached and, if it is
to be weighed, washed further with water and then with alcohol and dried
at 70°.

The residual liquid is then heated—the anode, sometimes covered with
manganese dioxide, being kept immersed—to destroy the ammonium car-
bonate formed by the decomposition of the ammonium oxalate, to redissolve
the manganese dioxide, and to reduce the volume to 60-70 c.c. The liquid
is then heated with 1-5 gram of chrome alum and 10 grams of ammonium
acetate and the hot solution filtered directly into the matte Classen capsule.
After 3 c.c. of ammonia (D 0-94) have been added, the liquid is mixed,
brought to 70-80° and subjected to electrolysis, the capsule being con-
nected with the positive pole. ND100 = 0-5-0-6 amp., voltage = 2-3,
temperature = 70-80°, duration = about 2 hours.

When the deposition is found to be complete by raising slightly the
level of the liquid, the disc functioning as cathode is lifted out and the
contents of the dish poured away, the deposited manganese dioxide being
carefully washed with water. The dish is then dried at 100° and heated
at a dark-red heat to transform the dioxide and the higher oxides into the
saline oxide, Mn304.

When cold, the dish is washed once more with water to remove any
chromic acid which may be included, again ignited and weighed rapidly
to prevent the manganese oxide from absorbing moisture : Mn304 x 0-7205
= Mn.

The electrolytic method certainly takes longer than the volumetric method,
but has the advantage of not requiring standard solutions and of being applicable
also in presence of chromium, cobalt, nickel and vanadium.

2.  Determination of the Carbon.—This is usually carried out by the
Corleis method (see Iron, i, a] or, better, by direct combustion in a current
of oxygen (see Iron, I, b).

3.  Determination of the Silicon.—When this is required, it may be
effected along with the determination of the manganese (see Determination
of silicon in iron, 2, 6).

4.  Determination of the  Phosphorus,  Sulphur  and Arsenic.—
These elements are estimated as in cast- or wrought-iron.

* *

The manganese content of ferro-manganeses may vary from 25 to 85% and
the carbon content from 5 to 7-5%, the two generally increasing together.
Ferro-manganeses contain also 0-5-2-5 % of silicon, small quantities of phosphorus
(0-1-0-4%) and minimal traces of sulphur, copper, etc.

Spiegeleisen contains 0-2-1-2% of silicon, 4-5% of carbon and 5-25% of
manganese, and sometimes, as impurities, small proportions of phosphorus and
sulphur. minute), this addition